Late Permian and Early Triassic evolution of the Northern Indian margin: carbon isotope and sequence stratigraphy Evolution de la marge indienne du Permien superieur au Trias inferieur: stratigraphie isotopique (carbone) et sequentielle

The Northern part of Great-India underwent an early rifting phase in the late Paleozoic, just at the end of the large scale Gondwanian glaciation. The beginning of the rifting processes is marked by large hiatus and discontinuities (para­ conformities) between the early or middle Paleozoic sedimen­ tary succession and the discontinuous middle-late Permian Traps and transgressive sediments. The Northern Indian passive margin consists of the present High and Lower Himalaya and a small part of the Indian craton and their sedimentary cover. The Permian rift shoulder is located in the Higher Himalaya, with part being in the underthrusted Lower Himalaya. The rim basin Oandward of the shoulder) is well developed in the Pottawar - Salt Range area. From the rifting to the beginning of the drifting stages (early late Permian to late early Triassic time), the sedi­ mentary evolution is characterised by three transgressive­ regressive (T-R) second order cycles, two in the late Permian and one in the early Triassic. The break-up of the rift occurred during the second cycle (late Dzhulfian). In the Salt Range area, these three T-R cycles have been subdivided in eight third order sequences, five sequences for the upper Permian and three for the lower Triassic. At the end of Permian, hiatuses, gaps and local erosion of part of the margin are direct consequences of a first order rela­ tive sea-level fall; this is also the time of the largest extinction event of the Phanerozoic that deeply affected the carbonate productivity and the stratal patterns. With the following world­ wide sea-level rise, a rapid and large scale transgression occurred in the early Triassic, well dated and recorded on the whole margin. High rate thermal subsidence gave way to gene­ ralized pelagic deposits about 2 My after the transgression. Profiles of whole rock inorganic carbon and oxygen isotopes from Guryul Ravine and Palgham sections in Kashmir, Nammal